About Generation of Terahertz Radiation Due to the Nonlinear Interaction of Gaussian and Hermite-Cosh-Gaussian Laser Beams in Collisional Plasma Background: Optimization and Field Profile Controlling

A theoretical model has been considered for describing the generation of terahertz (THz) radiation via nonlinear interaction of Gaussian and Hermite-cosh-Gaussian laser beams in a plasma background. By using Maxwell's equations and taking into account the collision approximation for the plasma medium, the amplitude of the emitted THz wave is obtained. The effective factors on THz wave amplitude, such as the laser beamwidth, decentered parameter, mode index, the plasma collision frequency, and the amplitude of density ripple, are studied. In this nonlinear phenomenon, the role of laser beamwidth is very important. It is found that the shape of generated THz radiation pattern can be tuned by the laser parameters. In addition, an optimized relation for achieving the maximum THz wave amplitude is proposed. Based on the proposed scheme, a normalized THz field amplitude of ~ 0.4 is achieved, which is much greater than the maximum amplitude of THz field obtained from the nonlinear interaction of two laser beams with the same profiles.